Is there an association between acute, subacute, and late genitourinary quality of life with prostate SBRT boost?

Emerging evidence demonstrates an association between acute and late genitourinary (GU) toxicity following prostate radiotherapy. However, this is not established following SBRT, and subacute toxicities may represent a transient and independent entity. We conducted a post-hoc analysis of the PROMETHEUS prospective phase II trial (ACTRN12615000223538) to investigate correlations among acute, subacute, and late GU QOL in patients who received SBRT as a virtual-high-dose-rate brachytherapy boost for prostate cancer.

The trial consisted of 151 men, with a median follow-up of 60 months. Relationships between acute (end of treatment [EOT]), subacute (12 months), and late (36 and 60 months) GU QOL changes were examined using EPIC-26 scores and minimal clinically important differences (MCID). Univariable and multivariable logistic regression were performed separately for incontinence, obstructive, and irritative domains.

On multivariable analysis, late incontinence MCID was associated with MCID at EOT (OR 3.55 [95% CI 1.42-8.92], p = 0.01) and 12 M (8.72 [3.53-21.56], p < 0.01). Prior TURP (6.11 [1.56-23.89], p = 0.01) and Rectafix versus SpaceOAR (2.6 [1.09-6.23], p = 0.03) were also associated with late incontinence. Late irritative MCID was associated with poor baseline irritative function (7.95 [1.71-36.91], p < 0.01) and subacute irritation (5.47 [2.11-14.18], p < 0.01). No associations were identified with late obstructive MCID.

This study identifies subsets of men who experience acute, subacute and late GU toxicity after prostate SBRT. Baseline or subacute irritative symptoms are predictors of longer-term irritation. Patients with prior TURP or baseline irritative symptoms may benefit from close assessment and intervention during follow-up.